Piston head with heat dam or barrier



June 25, 1963 F. ZOLLNER 3,094,903

PISTON HEAD WITH HEAT DAM 0R BARRIER Filed Aug. 17, 1961 4 Sheets-Sheet 1 June 25, 1963 F. ZOLLNER 3,094,903

PISTON HEAD WITH HEAT DAM OR BARRIER Filed Aug. 17, 1961 4 Sheets-Sheet 2 INVENTOR. )964 2'0 /777@ 7' a EMW W June 25, 1963 F. ZOLLNER 3,094,903

PISTON HEAD WITH HEAT DAM OR BARRIER Filed Aug. 17, 1961 4 Sheets-Sheet 3 m/ if m.

INVENTOR,

June 25, 1963 F. ZOLLNER 3,094,903

" PISTON HEAD WITH HEAT DAM OR BARRIER File'd Aug. 17, 1961 4 Sheets-Sheet 4 E; LE1

INVENTOR. f5? 6 70 Z7776 7'.

United States Patent I 3,094,903 Patented June 25, 1963 i ii C 3 094 903 PISTQN HEAD WITII HE AT DAM R BARRIER Fred Zollner, Fort Wayne, Ind., assignor to Zollner Corporation, Fort Wayne, Ind., a corporation of Minnesota Filed Aug. 17, 1961, Ser. No. 132,078 15 Claims. (Cl. 92-222) This invention relates to pistons for internal combustion engines, such pistons in practice generically being provided with a piston head and a depending skirt having aligned wrist pin bosses or openings immediately below the head. The piston head is customarily formed with a suitable number of annular ring grooves to receive any conventional piston or compression rings, the upper ring groove being located a substantial distance below the top surface of the head, thereby providing the piston head with a top substantially annular land between the top ring groove and the top of the piston head. The lower ring groove, at least where a series or selected number of grooves are provided, is located as customary a desired distance above the wrist pin bosses or openings.

An important object and feature of the present invention reside in the provision of a piston head having incorporated in the annular land between the top ring groove and the transverse top surface or facing of the piston an annular heat dam or thermal barrier formed by means of a ring insert or annular band preferably fixedly cast in place under radial compression at the time of molding the piston and thereby anchored under preload and hence disposed under what may be characterized as hoop tension. This heat dam or barrier functions to rectrict, impede or greatly block the normal temperature flow downwardly and past the same from the top of the piston head.

The important functional impeding, restriction or very marked deceleration of temperature flow toward the upper piston ring or groove results (1) in desirably increasing the temperature of that portion of the land or piston head above the heat darn or thermal barrier thereby reducing by burning or combustion the extent of formation of undesirable solids from the gaseous products of combustion;

. and (2) in lowering the temperature of that portion of the land or piston head below the heat dam or barrier and above the upper ring groove thereby producing a material or significant reduction in the extent to which undesirable solids are formed and accumulate consequent to the burning of the cylinder lubricating oil.

As representative of the present invention a number of aspects thereof have been selected for exemplary purposes and herein illustrated as embodiments of the invention. In one embodiment, such as exemplified in FIGURES 1 to 3, the heat or thermal dam or barrier ring is formed with a series of annularly spaced inwardly projecting flanges which are alternately directed upwards and down- 1 wardly and separated by a series of notches, the opposed fedges of each notch preferably tapering in an inward direction in partially converging relation. In a second illustrated embodiment, such as exemplified in FIGURES 4 to 6, the heat or thermal barrier ring, also i disposed as in all embodiments intermediate the upper ring groove and top of the piston, is formed with a series 1 of annularly spaced inwardly projecting flanges which lie in substantially coplanar relation. As in the previous embodiment the opposed edges of eachnotch between adjacent flanges oppositely taper in an inward direction in a partially converging fashion.

In an embodiment shown, for example, in FIGURES 7 and 8, there is illustrated a heat or thermal barrier ring or annular band which is provided with coplanar upper and lower surfaces. If desired for the purpose of anchoring assistance against any possible circumferential displacement during any operating condition the inner annular edge of the ring or band may be slightly beveled or tapered preferably in a downward direction.

As clearly exemplified in one embodiment, illustrated for example in FIGURES 9 and 10, the heat or thermal barrier ring with coplanar upper and lower surfaces has What may be termed a scalloped or irregular inner edge, such as one that is undulated or wavy with opposed reversely inclined portions, thereby performing an effective anchoring function.

In other exemplified embodiments, such as illustrated in FIGURES 11 to 13, the heat or thermal barrier ring has in one instance an upper surface tapered outwardly and downwardly providing a single taper anchoring wedge, and has in a second instance both upper and lower surfaces tapered outwardly in opposed directions thereby providing a double taper anchoring wedge.

As exemplified in another selected embodiment, such as illustrated in FIGURES 14 and 15, the heat or thermal barrier ring is formed with an annular continuous crimp or offset intermediate the inner and outer edges of the ring, this so-called crimp providing a shallow channel or groove which leaves these opposed inner and outer edges in coplanar relation.

The heat barrier ring of any of the embodiments, or otherwise, may be formed with either one eccentric inner edge portion or opposed eccentric inner edge portions, thus affording or ensuring a quite effective anchoring function. An illustration of the foregoing appears in FIGURE 16.

From the foregoing it will be markedly apparent that a piston for an internal combustion engine fabricated with an annular heat or thermal dam or barrier between the upper piston ring groove and the top surface of the piston head achieves important advantages throughout wide variations in engine operation not heretofore gained and in particular by aluminum alloy pistons in general use. Where the heat barrier ring insert, as preferred in most instances, is formed of steel or equivalent ferrous alloy, it may often be desired to reduce the thermal ring slightly in diameter so as to obviate direct contact with the cylinder wall, although in such instances projecting inwardly substantially or approximately from the outer annular surface of the head. However, in connection with certain types of engines it may be desired .to ensure direct contact with the cylinder wall, such for instance as to avoid any slight increase in oil consumption. In such cases a metal alloy other than steel may be employed in the ring, which alloy would be compatible with the cylinder so as to function effectually in close contact relation thereto under all conditions of engine operation.

In the preferred construction an aluminum alloy piston, conventionally termed as aluminum piston, is utilized to gether with a heat dam or thermal barrier ring of steel. It will, of course, be understood, and within the spirit of the present invention, that where desired other ferrous as well as nonferrous metals may be utilized as dictated by conditions of use and operation.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views. FIGURE 1 is a central vertical sectional view of a piston embodying the present invention.

FIGURE 2 is a plan view of the heat barrier ring embodied in the piston shown in FIGURE 1.

FIGURE 3 is a sectional view taken through lines 3-3 of FIGURE 2 looking in the direction of the arrows.

FIGURE 4 is a fragmentary central vertical sectional view of a piston similar to the piston of FIGURE 1, h-av ing a heat barrier ring according to a second embodiment of the invention.

FIGURE 5 is a plan view of the ring embodied in the piston of FIGURE 4.

FIGURE 6 is a sectional view taken through lines 6-6 of FIGURE 5 looking in the direction of the arrows.

FIGURE 7 is a fragmentary sectional view of a piston similar to the piston of FIGURE 1 having a heat barrier ring according to a third embodiment.

FIGURE 8 is a central transverse sectional view of the ring incorporated in the piston of FIGURE 7.

FIGURE 9 is a sectional view taken through lines 99 of FIGURE 10 looking in the direction of the arrows.

FIGURE 10 is a plan view of a ring according to a fourth embodiment.

FIGURE 11 is a fragmentary sectional view of a piston similar to the piston of FIGURE 1 having a heat barrier ring formed in accordance with a fifth embodiment.

FIGURE 12 is a central transverse sectional view of the ring incorporated in the piston of FIGURE 11 and having a single taper anchoring wedge.

FIGURE 13 is a view similar to FIGURE 12 illustrating a double taper anchoring Wedge.

FIGURE 14 is a fragmentary sectional view of a piston similar to the piston of FIGURE 1 having a heat barrier ring according to a further embodiment.

FIGURE 15 is a central transverse sectional view of the ring incorporated in the piston of FIGURE 14.

FIGURE 16 is a plan view of a heat barrier ring illustratin-g a still further embodiment.

Before explaining in detail the present invention, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of 'being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

For exemplary purposes there is illustrated in FIG- URE 1 of the drawings, and in part in FIGURES 4, 7, 11 and 14, a suitably selected piston, generally indicated at 20, which is cast in one piece in a permanent mold and is preferably of an aluminum alloy. The piston is provided with a head 21 and a depending skirt 22 formed with the usual opposed wrist pin bosses having aligned wrist pin openings 23. The piston head is formed with a suitable number of annular ring grooves 24- to receive the piston rings, the upper ring groove fbeing indicated at 24a.

With reference to the embodiment illustrated in- FIG- URES 1 to 3, there is provided a heat or thermal barrier ring 25 cast in place in the piston head under radial compression at the time of molding the piston. As clearly shown in FIGURE 1, the ring 25 is disposed above and in spaced relation to the upper ring groove 24a and also spaced a selected distance below the top 29 of the piston head. In this embodiment the ring 25 is integrally formed with a series of circumferentially spaced, inwardly projecting flanges. In alternate relation the flanges 26 are tapered or directed upwardly and the flanges 27 are tapered or directed downwardly. Arcuate notches 28 are formed between the pairs of flanges and the opposed edges of each notch taper inwardly in partially converging relation.

It will be readily seen that by virtue of the construction in the foregoing embodiment, the heat darn or barrier ring 25 is effectively anchored in interlocking relation with the piston head 21 and is disposed so as to ensure marked restriction, impeding or deceleration of heat transmission downwardly from the top of the piston head to the upper ring groove and the piston ring .disposed therein during engine operation.

In the embodiment illustrated in FIGURES 4 to 6, there is provided a heat or thermal barrier ring 30 cast in place, as in all embodiments, in the piston head under radial compression during the molding operation and disposed between and fully spaced from the top 29 of the duction from the hot aluminum and at temperatures above piston head and the upper ring groove 24a. In this embodiment the thermal barrier ring has substantially coplanar inwardly directed portions or flanges 31 separated by notches 32 with the opposed reversely inclined edges 33 of each notch tapering inwardly in partially converging relation. By reason of this construction the ring 30 is effectively anchored in the piston head and functions in the manner hereina bove fully set forth.

In the embodiment of FIGURES 7 and 8, the heat or thermal barrier ring is shown at 34. This ring is cast in place at the same locality in the piston head as the rings of all other illustrated embodiments, the ring 34 having coplanar upper and lower surfaces 35 with preferably a tapered inner edge and functioning in the same manner as above set forth.

In FIGURES 9 and 10 there is shown at 36 another embodiment of heat or thermal barrier ring. In this exemplifioation the ring has a scalloped or undulated inner edge 37 comprising notch-like portions 38 forming inwardly projecting tapered portions 39 having opposed reversely inclined inner edges. It will be apparent that by virtue of this construction the ring 36 also will be anchored in the piston head between and in fully spaced relation to the upper ring groove 24a and piston head top 29.

With reference to FIGURES 11 and 12, the heat or thermal barrier ring above referred to is shown at 40, this ring having the upper tapered surface 41 providing a single anchoring wedge in association with the lower flat surface 42 of the ring.

In FIGURE 13 the heat barrier ring 43 is formed with an upper outwardly tapered surface 44 corresponding and companion to the tapered surface 41 in FIGURE 12. In this embodiment the ring 43 is formed with a lower outwardly tapered surface 45 thereby providing a double taper anchoring wedge.

With respect to FIGURES 14 and 1 -5, the heat barrier ring is shown at 46. This ring is centrally crimped or offset intermediate its edges at 47, thereby providing an anchoring groove or channel 48 having relatively tapered portions.

With reference to the heat barrier ring 49 illustrated in the embodiment of FIGURE 16, the opposed eccentric inner edges of the ring are shown in full lines at 50, 51. The normal circular inner edge before machining the ring into eccentric form is shown by the broken dotted line 52. The eccentricity or eccentric taper of the inner edge of this ring effectively functions to anchor or assist in anchoring the ring in the piston head after the casting operation. It will be understood that this eccentric shaping of the inner edge of the heat or thermal barrier ring, disposed at the locality shown in any of FIGURES 1, 4, 7, 11 and 14 and above described, may be applied to any of the rings shown in the several embodiments.

It is important to note with respect to the several embodiments that the thermal barrier ring insert is anchored in the piston under preload and placed under such radial compression as is equivalent to the difierence between the coeflicient of expansion of the aluminum piston alloy and the steel or other metal alloy of the insert. As a consequence, any bimetallic expansion problem at any of the various operating temperatures to which the piston head is subjected is eliminated thereby ensuring a substantially constant non-varying relationship between the i barrier ring and the adjacent portions of the piston head 1 irrespective of the difference in expansion of the aluminum alloy of the piston and the ferrous or non-ferrous metal of the ring.

During the casting operation and as the aluminum of the piston cools and solidifies it contracts at its own contraction rate, which is approximately twice the contraction rate of the ferrous barrier ring insert. This insert during the cooling period increases in temperature by conor in the neighborhood of 600 F. the cooling aluminum and ring insert arrive at substantially the same temperature. At such time the aluminum, while contracting in the cooling process, has sufiicient strength to compress the ring insert which is contracting at its own contraction rate. Hence, the amount of compression forces exerted at the ring insert corresponds to the difierence in the normal contraction rate of the aluminum piston and the normal contraction rate of the ring insert.

From the foregoing it will be apparent that during engine operation the aluminum piston head expands at its normal rate and, in effect, carries the ring insert with it. Inasmuch as the insert is in compression to the extent of the difference in the amount of expansion of the piston head that might occur, no relative movement will take place between the barrier ring insert and the piston head at the locality of this ring.

I claim:

1. A piston for an engine including a head having ring groove means including an uppermost annular ring groove for the reception of a separate removable piston ring and an annular land disposed between said ring groove and the top of the piston head, a substantially annular heat barrier ring immovably mounted within an outer groove in said head and dividing the head into two sections comprising an upper annular portion of said land disposed in its entirety above the barrier ring and a lower annular portion disposed below the barrier ring and in its entirety above said ring groove, said barrier ring having outer and inner edge portions disposed in a single plane intersecting the same and lying substantially parallel to the ring groove, and said barrier ring providing such restriction to normal temperature flow during piston operation as to etfect an increase in the temperature of said upper annular land portion and a decrease in the temperature of said lower land portion.

2. A piston for an engine including an aluminum head having ring groove means including an uppermost annular ring groove for the reception of a separate removable piston ring and an annular land disposed between said ring groove and the top of the piston head, a substantially annular steel heat barrier ring immovably mounted within an outer groove in said head and dividing the head into two sections comprising an upper annular portion of said land disposed in its entirety above the barrier ring and a lower annular portion disposed below the barrier ring and in its entirety above said ring groove, said barrier ring having outer and inner edge portions disposed in a single plane intersecting the same and lying substantially parallel to the ring groove, and said barrier ring providing such restriction to normal temperature flow during piston operation as to effect an increase in the temperature of said upper annular land portion and a decrease in the temperature of said lower land portion, said barrier ring being fixedly cast in place under inwardly directed radial compression and thereby anchored under preload.

3. A piston for an engine according to claim 1 wherein said barrier ring has means effecting an anchoring interlock with the piston head.

4. A piston for an engine according to claim 1 wherein said barrier ring has an eccentric inner edge portion effecting an anchoring interlock with the piston head.

5. A piston for an engine according to claim 1 wherein said barrier ring has a portion or portions thereof tapered 3 tapered to ensure an anchoring interlock with the piston head.

8. A piston for an engine according to claim 1 wherein said barrier ring has outer and inner portions thereof tapered to ensure an anchoring interlock with the piston head.

9. A piston for an engine including a head having ring groove means including an uppermost annular ring groove for the reception of a separate removable piston ring and an annular land disposed between said ring groove and the top of the piston head, a substantially annular heat barrier ring immovably mounted within a groove in said head and dividing the head into two sections comprising an upper annular portion of said land disposed in its entirety above the barrier ring and a lower annular portion disposed below the barrier ring and in its entirety above said ring groove, said barrier ring providing such restriction to normal temperature flow during piston operation as to effect an increase in the temperature of said upper annular land portion and a decrease in the temperature of said lower land portion, said barrier ring having inner annularly spaced projecting portions reversely tapered upwards and downwardly to ensure an anchoring interlock with the piston head.

10. A piston for an engine including a head having ring groove means including an uppermost annular ring groove for the reception of a separate removable piston ring and an annular land disposed between said ring groove and the top of the piston head, a substantially annular heat barrier ring immovably mounted within a groove in said head and dividing the head into two sections comprising an upperannular portion of said land disposed in its entirety above the barrier ring and a lower annular portion disposed below the barrier ring and in its entirety above said ring gnoove, said barrier ring providing such restriction to normal temperature flow during piston operation as to effect an increase in the temperature of said upper annular land portion and a decrease in the temperature of said lower land portion, said barrier ring having inner annularly spaced coplanar projecting portions, the inner opposed edges of adjacent portions being reversely inclined.

11. A piston for an engine including a head having ring groove means including an uppermost annular ring groove for the reception of a separate removable piston ring and an annular land disposed between said ring groove and the top of the piston head, a substantially annular heat barrier ring immovably mounted within a groove in said head and dividing the head into two sections comprising an upper annular portion of said land disposed in its entirety above the barrier ring and a lower annular portion disposed below the barrier ring and in its entirety above said ring groove, said barrier ring providing such restriction to normal temperature flow during piston operation as to eifect an increase in the tempera ture of said upper annular land portion and a decrease in the temperature of said lower land portion, said barrier ring having the upper surface thereof tapered outwardly and downwardly to provide a taper anchoring wedge.

12. A piston for an engine including a head having ring groove means including an uppermost annular ring groove for the reception of a separate removable piston ring and an annular land disposed between said ring groove and the top of the piston head, a substantially annular heat barrier ring immovably mounted Within a groove in said head and dividing the head into two sections comprising an upper annular portion of said land disposed in its entirety above the barrier ring and a lower annular portion disposed below the barrier ring and in its entirety above said ring groove, said barrier ring providing such restriction to normal temperature flow during piston operation as to effect an increase in the temperature of said upper annular land portion and a decrease in the temperature of said lower land portion, said barrier ring having the lower surface thereof tapered outwardly and upwards to provide a taper anchoring wedge.

13. A piston for an engine including a head having ring groove means including an uppermost annular ring groove for the reception of a separate removable piston ring and an annular land disposed between said ring groove and the top of the piston head, a substantially annular heat barrier ring immovably mounted within a groove in said head and dividing the head into" two sections comprising an upper annular portion of said land disposed in its entirety above the barrier ring and a lower annular portion disposed below the barrier ring and in its entirety above said ring groove, said barrier ring providing such restriction to normal temperature flow during piston operation as to elfect an increase in the temperature of said upper annular land portion and a decrease in the temperature of said lower land portion, said barrier ring having a substantially coplanar scalloped or undulated inner edge.

14. A piston for an engine including a head having ring groove means including an uppermost annular ring groove for the reception of a separate removable piston ring and an annular land disposed between said ring groove and the top of the piston head, a substantially annular heat barrier ring immovably mounted within a groove in said head and dividing the head into two sections comprising an upper annular portion of said land disposed in its entirety above the barrier ring and a lower annular portion disposed below the barrier ring and in its entirety above said ring groove, said barrier ring providing such restriction to normal temperature flow during piston operation as to effect an increase in the temperature of said upper annular land portion and a decrease in the temperature of said lower land portion, said barrier ring forming an annular channel or groove with opposed edges disposed in substantially coplanar relation.

15. A piston comprising in substantially finished condition -a head having a top annular piston ring groove and a transverse top facing, and a substantially annular heat barrier ring insert immovably cast in said head in wholly-spaced relation to said top facing and to said piston ring groove, said barrier ring projecting inwardly substantially or approximately from the outer annular surface of said head, said barrier ring having opposed eccentric inner edges.

References Cited in the file of this patent UNITED STATES PATENTS 2,255,006 Graham Sept. 2, 1941 2,970,020 Johnson Jan. 31, 1961 FOREIGN PATENTS 1,060,8 13 France Nov. 25, 1953 195,181 Austria Aug. 15, 1955 

1. A PISTON FOR AN ENGINE INCLUDING A HEAD HAVING RING GROOVE MEANS INCLUDING AN UPPERMOST ANNULAR RING GROOVE FOR THE RECEPTION OF A SEPARATE REMOVABLE PISTON RING AND AN ANNULAR LAND DISPOSED BETWEEN SAID RING GROOVE AND THE TOP OF THE PISTON HEAD, A SUBSTANTIALLY ANNULAR HEAT BARRIER RING IMMOVABLY MOUNTED WITHIN AN OUTER GROOVE IN SAID HEAD AND DIVIDING THE HEAD INTO TWO SECTIONS COMPRISING AN UPPER ANNULAR PORTION OF SAID LAND DISPOSED IN ITS ENTIRETY ABOVE THE BARRIER RING AND A LOWER ANNULAR PORTION DISPOSED BELOW THE BARRIER RING AND ITS ENTIRETY ABOVE SAID RING GROOVE, SAID BARRIER RING HAVING OUTER AND INNER EDGE PORTIONS DISPOSED IN A SINGLE PLANE INTERSECTING THE SAME AND LYING SUBSTANTIALLY PARALLEL TO THE RING GROOVE, AND SAID BARRIER RING PROVIDING SUCH RESTRICTION TO NORMAL TEMPERATURE FLOW DURING PISTON OPERATION AS TO EFFECT AN INCREASE IN THE TEMPERATURE OF SAID UPPER ANNULAR LAND PORTION AND A DECREASE IN THE TEMPERATURE OF SAID LOWER LAND PORTION. 